Add detailed message to changelog workflow (#12979)

[umaarov]

This PR creates a new troubleshooting guide to help new contributors understand and fix common CI/CD failures, as requested in issue #12979.

What's included:

• A new guide at .github/WORKFLOW_TROUBLESHOOTING.md that covers DCO, Changelog, Gradle, and Backport checks.
• An entry in CHANGELOG.md for this change.

Closes #12979

[andrross]

I'm more inclined to make things self-documenting rather than add text to a markdown file that a contributor may or may not be able to find. For example, the DCO workflow is clickable, and the resulting page gives a link that says View more details on DCO. In case of a DCO failure it provides detailed instructions about how to fix your commit. I'm not sure it's helpful to duplicate that information in other places.

For the other workflows, I'd love to see if we can find ways to provide the same basic experience: I see a failed workflow in my PR, I click on the workflow link, I get details about what the failure means that allows me to understand it and fix it.

[umaarov]

Hi @andrross @peternied,
Just wanted to follow up gently on this PR. I updated it last week based on the feedback and was hoping to get the workflow runs approved when you have a moment. Thanks again for your time and guidance!